1. Field of the Invention
The present invention relates to an organic semiconductor device such as an organic thin-film transistor, and a manufacturing method thereof.
2. Description of the Related Art
Typical active-matrix flat-panel displays (FPD), such as a liquid crystal display and an organic electroluminescence (EL) display, have employed switching elements referred to as thin-film transistors (TFT) in order to drive pixels.
Organic thin-film transistors are attracting attention in recent years as such switching elements used for driving pixels in electronic paper and next-generation FPDs. Hence, various organic thin-film transistors have been introduced (Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2007-273957, for example).
Described below is a conventional organic thin-film transistor disclosed in Patent Reference 1, with reference to FIGS. 13A and 13B. FIG. 13A is a plan view of the conventional organic thin-film transistor having a drain electrode, a source electrode, and a gate electrode. FIG. 13B is a cross-sectional view of the conventional organic thin-film transistor taken from line G-G′ of FIG. 13A.
As shown in FIGS. 13A and 13B, a conventional organic thin-film transistor 101 includes the following: a substrate 111, a ring-like gate electrode gate electrode 112, a ring-like drain electrode 114 formed above the gate insulation film 113, and a ring-like source electrode 115 formed above the gate insulation film 113 and around the drain electrode 114.
The conventional organic thin-film transistor 101 has an organic semiconductor layer 117 (i) formed above a region including the drain electrode 114 and the source electrode 115, and (ii) fill a space between the drain electrode 114 and the source electrode 115. In order to have the organic semiconductor layer 117 formed a solution including an organic semiconductor material is applied over the drain electrode 114.
Moreover, the conventional organic thin-film transistor 101 has a passivation film 120 formed over the organic semiconductor layer 117 in order to inhibit deterioration of the organic semiconductor layer 117 caused by water and oxygen in the air.
Regarding the conventional organic thin-film transistor 101, however, the passivation film 120 formed over the organic semiconductor layer 117 covers the entire organic thin-film transistor 101. Thus, the passivation film 120 is not suitable enough as a protective film dedicated to the organic semiconductor layer 117.
Hence, the conventional organic thin-film transistor 101 has a problem in that the passivation film 120 cannot prevent water and oxygen from entering the organic semiconductor layer 117, resulting in deterioration of the organic semiconductor layer 117 and variations in threshold voltage “Vt”.
The present invention is conceived in view of the above problem and has as an object to introduce an organic semiconductor device and a manufacturing method thereof which can provide effective protection for an organic semiconductor layer to prevent deterioration of the organic semiconductor layer.